The breeding distribution of western burrowing owl is experiencing an intriguing southward shift, contrary to the predictions of climate change. To determine the breeding dispersal patterns underlying this distributional change, we developed 11 novel polymorphic microsatellite loci for the species. We tested these loci in two burrowing owl breeding populations, one from central Sinaloa, Mexico, and one from the Central Valley of California, USA.
All loci were at Hardy-Weinberg equilibrium, except two loci for the California population. Expected heterozygosity was relatively high (HE = 0.813, range 0.515-0.942). Average number of alleles was 11.64 (range 5-25). We found no evidence of linkage disequilibrium for any pairwise tests between loci.
The Western Burrowing Owl (Athene cunicularia
hypugaea) is a grassland specialist distributed
throughout w. North America, primarily in open
areas with short vegetation and bare ground in
desert, grassland, and shrub-steppe environments.
Burrowing Owls are dependent on the presence
of fossorial mammals (primarily prairie dogs and
ground squirrels), whose burrows are used for
nesting and roosting. Burrowing Owls are protected
by the Migratory Bird Treaty Act in the United
States and Mexico. They are listed as Endangered in
Canada and Threatened in Mexico. They are
considered by the U.S. Fish and Wildlife Service
(USFWS) to be a Bird of Conservation Concern at
the national level, in three USFWS regions, and in
nine Bird Conservation Regions . At the state level,
Burrowing Owls are listed as Endangered in
Minnesota, Threatened in Colorado, and as a Species
of Concern in California, Montana, Oklahoma,
Oregon, Utah, Washington, and Wyoming.
Burrowing Owls historically bred from sc. and sw.
Canada southward through the Great Plains and w.
United States and south to c. Mexico. Although the
historical breeding range is largely intact, range
contractions have occurred primarily at peripheral
regions, in s. Canada, the ne. Great Plains, and parts
of California and the Pacific Northwest. Burrowing
Owls winter in the sw. and sc. United States,
throughout Mexico, and occasionally as far south
as Panama.
Populations of Burrowing Owls have declined in
several large regions, notably in the ne. Great Plains
and Canada. However, estimates of population
trends in many regions are generally inconclusive
due to small samples sizes and high data variability.
Population trends as determined from North
American Breeding Bird Survey (BBS) data were
inconsistent, with some regions exhibiting positive
trends and other regions exhibiting negative trends.
When taken as a whole, the BBS indicated an area
of generally declining populations in the northern
half of the Great Plains, and generally increasing
populations in the interior U.S. and in some
southwestern deserts. The Christmas Bird Count
indicated a significant population decline in
California (1966-1989). Local surveys have detected
declining populations and/or range reductions in
California, Iowa, Kansas, Minnesota, Nebraska,
New Mexico, North Dakota, Oklahoma, Oregon,
South Dakota, Texas, Washington, and throughout
the range of the species in Canada.
Primary threats across th
The Spring Canyon/Goat Mesa vernal pools complex (J16-18) were identified by the adopted Recovery
Plan for Vernal Pools of Southern California (USFWS 1998) as necessary to stabilize populations of the
following endangered and threatened species: E. aristulatum, P. nudiuscula, N. fossalis, O. californica, B.
sandiegonensis, and S. woottoni. The Management Strategic Plan for Conserved Lands in Western San
Diego County (SDMMP) also lists other MSP species historically found onsite at Spring Canyon/Goat Mesa
including D. variagata, M. minimus, S. hammondii, and A. cunicularia. Otay Mesa/Goat Mesa Open Space
has also had recent recorded occurrences of Western Burrowing Owl, including a pair of owls observed
using artificial burrows as recently as December 29, 2017 before the grant project started.
We report on the fifth year’s progress in a multi-year program with the goal of developing a strategy to support the recovery of Western burrowing owls (BUOW; Athene cunicularia hypugaea) and their grassland ecosystem in San Diego County. Current BUOW management is dependent on continued human intervention and may not be self-sustaining. Because the California ground squirrel (Otospermophilus beecheyi) is a keystone species that helps engineer California grassland ecosystems and provides critical resources for BUOW, re-establishment of this species is a crucial component of any sustainable recovery plan for BUOW and the larger ecosystem.
The main components of the program in 2015 consisted of work on both BUOW and California ground squirrel. For squirrels, we continued monitoring two previously established studies: (1) the experimental manipulation of grassland habitat structure and squirrel translocation to better support the persistence of ground squirrels, and (2) a pilot manipulation of natural squirrel dispersal into newly grazed pasture, using the addition of cover piles to attract squirrels into unoccupied habitat. In 2015, BUOW efforts continued to focus on understanding the ecological drivers and anthropogenic threats influencing BUOW population performance in San Diego County, as well as development of a new habitat suitability model for BUOW. These efforts were conducted collaboratively with California Department of Fish and Wildlife, San Diego Management and Monitoring Program, and other agency partners.
We report on the third year's progress in a multi-year program with the goal of developing a model program to assist with the recovery of Western burrowing owls (BUOW; Athene cunicularia hypugaea) and their grassland ecosystem in San Diego County. Current BUOW management is dependent on continued human intervention and may not be self-sustaining. Because the California ground squirrel (Otospermophilus beecheyi) is a keystone species that helps engineer California grassland ecosystems and provides critical resources for BUOW, re-establishment of this species is a crucial component of any sustainable recovery plan for BUOW and the larger ecosystem. Over time we plan to develop a set of protocols and strategies that can be adopted by managers in San Diego County and in other areas where BUOW conservation management is warranted. Our long-term goal is to assist in the establishment of a more natural grassland ecosystem in San Diego County by re-establishing ground squirrels and, ultimately BUOW. The work described here is the projection of the San Diego Zoo Institute for Conservation Research (ICR) and its partners, in particular, its research collaborators at San Diego State University. In 2013, we made progress towards three objectives: 1) use of translocation as a tool to establish California ground squirrels as ecosystem engineers, 2) developing methodology for monitoring natural squirrel dispersal into managed habitat at Rancho Jamul, 3) determining key habitat associations for California ground squirrels, and 4) monitoring BUOW population and nesting ecology in south San Diego County.